This invention relates to a process and apparatus for biological treatment of waste liquid. In a preferred aspect, the invention relates to a process and apparatus for biological treatment of the liquid fraction of separated pig manure by an upflow aerobic blofilter and to the coating of the solid fraction by powder zeolite. The process and apparatus according to the invention may also be used for treating waste industrial water.
The most widely used way today to manage pig manure is through storage in lagoons or concrete reservoirs and land spreading in the Spring and the Fall. For pig farms with sufficient cultivated land nearby, this way of managing the manure is appropriate, as long as the soil is not too permeable and does not allow pollutants in the manure to percolate through the soil and contaminate the subsurface waters.
Land spreading of the solid pig manure, containing high concentrations of ammonia results in leaching of ammonia and other contaminants when it rains. In order to allow land spreading of solid pig manure, some means of fixation of the nitrogenous compounds is required.
In areas of concentration of pig farms, an excess of manure versus available land for apreading exists and conventional methods of managing are inadequate. In such surplus areas, different aerobic or anaerobic systems for biological treatment of the pig manure have been installed in the past, but these installations do not always function property.
The main problems associated with aerobic processes, such as aerated lagoons, activated sludge or sequential batch reactors, lie in the inefficiency of the existing aeration systems, and in the fact that both the solid and liquid components of pig manure are treated together biologically. Aerobic biofilter systems may be prone to clogging, particularly when activated charcoal or clay-based media are used. Anaerobic systems require insulation and heating of the reactors In order to allow adequate completion of the biochemical reactions, particularly during colder weather.
In addition, any of these systems require very skilled manpower to operate, which is rarely adequately available in remote agricultural areas.
The result is often a failure of the conventional biological treatment processes.
The liquid fraction of farm and industrial waste can often be used rather than merely disposed of. For example, pig manure can be used for pig farm floor cleaning and other uses, as long as sufficient biological degradation of the organic and inorganic pollutants therein has occurred. The aerobic upflow biofilter described herein is an appropriate way to achieve this degradation.
One feature of the present invention is to provide a process and an apparatus for treating farm and industrial waste which are very efficacious and which do not require skilled manpower to operate.
Another feature of the present invention is to provide a process for treating the liquid fraction of such waste with an aerobic upflow biofilter to substantially reduce pollutants therein.
Another feature of the present invention is to provide a process for treating the solid fraction of such waste with zeolite in order to release the ammonia frown the manure.
In accordance with the features of the present invention, the liquid and solid fractions of the farm or industrial waste are first separated and then treated separately. The liquid fraction is treated in an aerobic biofilter system in which a liquid waste fraction and air are passed upflow through a reactor with a perforated media. This media is porous and is designed to reduce clogging by suspended material in the manure, but allow accumulation of biomass within the biofilter and thereby induce high oxygen transfer.
The solid fraction of the pig manure is accumulated and is mixed with powder zeolite. The affinity of ammonia for zeolite encourages the exchange, fixation and slow subsequent release of ammonia from this fraction.
Accordingly, the present invention provides a liquid waste treatment apparatus which comprises:
(a) a container having a top end and a closed bottom end;
(b) a first inlet on the container proximal to the closed bottom end for introducing liquid waste;
(c) a second Inlet on the container proximal to the closed bottom end for introducing oxygen-containing gas;
(d) a first outlet on the container proximal to the top end for removing treated liquid waste;
(e) a second outlet on the container proximal to the closed bottom end for purging solid or semi-solid residue;
(f) a rigid or semi-rigid perforated media occupying at least part of the container between the top end and the bottom end; and
(g) means for forcing the liquid waste through the media from the first inlet to the first outlet.
The present invention further provides a process for treating liquid waste in an apparatus as defined above, which process comprises:
(a) introducing liquid waste into the container through the first inlet;
(b) introducing oxygen-containing gas into the container through the second inlet;
(c) forcing the liquid waste through the media whereby the media provides a platform for aerobic microbial degradation of the liquid waste;
(d) recovering treated liquid waste from the first outlet;
and
(e) intermittently purging solid or semi-solid residue through the second outlet.